Active voltage snubber and voltage converter

Abstract

An active voltage snubber includes a ground terminal and an input terminal, and a snubber capacitor. A snubbing-activation device is designed to connect the input terminal to a second terminal of the snubber capacitor with a view to charging the snubber capacitor via this second terminal. Also included is a discharging switch for discharging the snubber capacitor, and a control circuit for controlling the discharging switch, which is designed to close the discharging switch so as to make the snubber capacitor discharge via its second terminal through the discharging switch. The control circuit is powered electrically by the snubber capacitor by being connected to the second terminal of the snubber capacitor so as to receive current from the snubber capacitor.

The invention claimed is: 
     
         1 . An active voltage snubber comprising:
 a ground terminal and an input terminal configured to receive an input voltage with respect to the ground terminal;   a snubber capacitor having a first terminal connected to the ground terminal;   a snubbing-activation device configured to connect the input terminal to a second terminal of the snubber capacitor when the input voltage delivered to the input terminal reaches a certain threshold, thereby charging the snubber capacitor via the second terminal;   a discharging switch for discharging the snubber capacitor, the discharging switch being connected to the second terminal of the snubber capacitor; and   a control circuit for controlling the discharging switch, which control circuit is configured to close the discharging switch so as to make the snubber capacitor discharge via the second terminal through the discharging switch;   wherein the control circuit is powered electrically by the snubber capacitor by being connected to the second terminal of the snubber capacitor so as to receive current from the snubber capacitor, and   wherein the control circuit is connected between the second terminal of the snubber capacitor and an output terminal, the output terminal being connected to an output capacitor, the output capacitor being connected between the output terminal and the ground terminal, and   wherein the discharging switch is configured to allow, when closed, the snubber capacitor to be discharged to the output capacitor.   
     
     
         2 . The active voltage snubber according to  claim 1 , wherein the control circuit comprises a comparator circuit configured to compare a voltage held by the snubber capacitor with at least one threshold, the control circuit being configured to control the discharging switch depending on the comparison. 
     
     
         3 . The active voltage snubber according to  claim 2 , wherein the at least one threshold comprises a first threshold and a second threshold lower than the first threshold, and wherein the control circuit is configured to close the discharging switch when the voltage of the snubber capacitor reaches the first threshold and to open the discharging switch when the voltage of the snubber capacitor reaches the second threshold. 
     
     
         4 . The active voltage snubber according to  claim 3 , wherein the control circuit comprises a supply circuit configured to deliver, from the snubber capacitor, a supply voltage to the comparator circuit. 
     
     
         5 . The active voltage snubber according to  claim 4 , wherein the supply voltage is delivered across the second terminal of the snubber capacitor and a floating reference terminal of the supply circuit. 
     
     
         6 . The active voltage snubber according to  claim 3 , wherein the discharging switch has a current-input terminal connected to the second terminal of the snubber capacitor and wherein the control circuit is configured to control the discharging switch via a control voltage applied across a control terminal of the discharging switch and the current-input terminal. 
     
     
         7 . The active voltage snubber according to  claim 3 , wherein the input terminal comprises two input terminals. 
     
     
         8 . The active voltage snubber according to  claim 2 , wherein the discharging switch has a current-input terminal connected to the second terminal of the snubber capacitor and wherein the control circuit is configured to control the discharging switch via a control voltage applied across a control terminal of the discharging switch and the current-input terminal. 
     
     
         9 . The active voltage snubber according to  claim 2 , wherein the input terminal comprises two input terminals. 
     
     
         10 . The active voltage snubber according to  claim 2 , wherein the snubbing-activation device comprises, for each input terminal, a diode having an anode connected to the input terminal and a cathode connected to the second terminal of the snubber capacitor. 
     
     
         11 . The active voltage snubber according to  claim 2 , further comprising an inductor connected to a current-output terminal of the discharging switch. 
     
     
         12 . A DC-DC voltage converter, comprising:
 a voltage rectifier comprising a switch; and   an active voltage snubber according to  claim 2 , the switch being connected between the input terminal and the ground terminal of the active voltage snubber.   
     
     
         13 . The active voltage snubber according to  claim 1 , wherein the discharging switch has a current-input terminal connected to the second terminal of the snubber capacitor and wherein the control circuit is configured to control the discharging switch via a control voltage applied across a control terminal of the discharging switch and the current-input terminal. 
     
     
         14 . The active voltage snubber according to  claim 1 , wherein the input terminal comprises two input terminals. 
     
     
         15 . The active voltage snubber according to  claim 1 , wherein the snubbing-activation device comprises, for each input terminal, a diode having an anode connected to the input terminal and a cathode connected to the second terminal of the snubber capacitor. 
     
     
         16 . The active voltage snubber according to  claim 1 , further comprising an inductor connected to a current-output terminal of the discharging switch. 
     
     
         17 . A DC-DC voltage converter, comprising:
 a voltage rectifier comprising a switch; and   an active voltage snubber according to  claim 1 , the switch being connected between the input terminal and the ground terminal of the active voltage snubber.   
     
     
         18 . The DC-DC voltage converter according to  claim 17 , further comprising:
 a transformer providing galvanic isolation;   a DC-AC converter connected to a primary of the transformer;   and wherein the rectifier is connected to a secondary of the transformer.